Ironwood Pharmaceuticals, Inc. (NASDAQ: IRWD) announced today that the Phase II clinical trial of linaclotide conducted in adults with opioid-induced constipation (OIC) met its primary endpoint. The OIC clinical trial was conducted jointly by Ironwood and a subsidiary of Allergan plc, Ironwood's co-development and co-commercialization partner for linaclotide in the United States.

"These top-line data demonstrate the positive effect of the guanylate cyclase-C (GC-C) agonist, linaclotide, on bowel movement frequency and other key endpoints in patients with OIC," said Dr. Michael Hall, senior vice president, clinical development of Ironwood. "As a pioneer and a recognized leader in GC-C agonists, we are committed to continued innovation with linaclotide, and we are very pleased with the results of this OIC trial."

Top-line data from the Phase II trial indicate that linaclotide-treated patients showed statistically significant improvement for the pre-specified primary endpoint: change from baseline in the 8-week Spontaneous Bowel Movement (SBM) frequency rate (SBMs/week), during the treatment period, for both doses tested, 145 mcg and 290 mcg, compared to placebo-treated patients. Consistent with previous Phase III trials of linaclotide in irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC), the most common adverse event reported in linaclotide-treated patients was diarrhea, with the majority being characterized as mild in severity.

This randomized, double-blind, placebo-controlled, multi-site Phase II clinical trial enrolled 254 adult patients with chronic, non-cancer pain who had been receiving a stable dose of an opioid analgesic and suffered from constipation, defined as fewer than three spontaneous bowel movements (SBMs) per week. Patients were randomized to receive 145 mcg of linaclotide, 290 mcg of linaclotide, or placebo for eight weeks.

Ironwood and Allergan will make a decision regarding advancement of the OIC program following a review of results from the linaclotide colonic release Phase IIb trial in adults with IBS-C and continued analysis of the full commercial opportunity. The companies expect data from the linaclotide colonic release Phase IIb trial in the second half of 2016.

Linaclotide is currently approved in the United States for the treatment of adults with IBS-C or CIC. It is also approved for adults with IBS-C or CIC in a number of other countries. Linaclotide is not currently approved for the treatment of OIC.